Dynamic-brake controller.



C. T. HENDERSON. DYNAMIC BRAKE CONTROLLER. APPLICATION FILED SEPT. 6, 1907. RENEWED FEB. 4, 1911.

1,002,687, Patented Sept. 5,1911

1 UNITED srnr .s ra'rnn'r cur os.

CLARK '1'. HENDERSON, Z MILWAUKEE, "WISGGNSIN, ASSIGNOR TO THE CUTLER- HAMMER MFG. 00., OF MILWAUKEE, WESGONSIN, A; CQEEGEATLEON 01 WISCONSIN.

DYNAMRt-IBBAKE GON'IE'TRULLER.

1,002,687. Application filed September 6, 1907, Serial Re.

To all whom it may concern:

Be it known that I, CLARK T. Hannnnson, a citizen of the United States, residing at .Milwaukee, inthe county of Milwaukee and 'State of Wisconsin, have invented new and useful Improvements in Dynamic-Brake Controllers, of which the following is a full,

i are adapted to cause the motor to become a generator and act as a dynamic brake when lt ls disconnected from clrcuit and is running under'the impetus it acquired while in operation. Such a result may be obtained by connecting a circuit across the armature, in which circuit is placed a resistance. 'lhe armature generates current and sends it through the circuit, which circuit may be called the braking circuit. The'resistance in.

the braking circuit is sufficient to prevent the current from becoming so great as to endanger the-armature. The braking force that is exerted by the armature depends upon its electrical load, which load is proportional to the braking current that is sent through the braking circuit. Inasmuch as the braking current decreases as the speed of the armature decreases, all other condi tions remaining the same, the braking force decreases in proportion to the decrease of speed of the armature. Accordingly there is a tendency for the period taken by the motor to come to rest to be prolonged.

One of the objects of my invention is to provide means whereby the braking current will have a high mean value throughout the period ofbraking the motor.

In order to attain the object of my invention, I provide means for varying the resistance in the braking circuit, which means are adapted to decrease the resistance in the braking circuit as the speed 01'- the armature decreases, whereby the bralc ing current is maintained at a high value throughout the braking period, and the braking period is thus reduced to a mi i-- mum. In order to prevent the resistance from being removed from circuit too rapidly, and at the same time be removed from circuit as rapidly as the conditions will al fipecification of Letters Patent.

low without endangering the armature, I provide a device by means of which the progress of removing the resistance from circuit will be arrested or retarded Whenever the braking current rises above a predetermined limit. y

In accordance with the preferred form of my invention 1 provide a electro-magnetically o ,erate resistance switches which control tie resistancein the braking circuit.

These switches, and also the resistances, may 'f'be the same as are used for starting the motor. The operation of these switches is so controlled that the same respond successively and thus gradually remove the resistance from circuit. In order to arrest the progressive operation of the switches it the braking current. becomes ab- Patented Sept. 5, 1911- 391,597. Renewed. February 4., 1811. Serial No. 606,647.

(plurality of normal and thus prevent further removal of the resistance from circuit until the current subsides to a normal value, Iprovide a magnetically operated relay device that responds to the braking cru'rent, or to a con dition which is controlled thereby. The relay device controls the circuits" of the operating windings of the resistance switches. It is operated by a winding preferably placed in the braking circuit in series with the armature. If the braking current rises above a predetermined point, the relay device operates and accordingly PI'GXQIltS further respondation of the operatin windings of the resistance switches until t e current subsides. In order to prevent the relay device from deenergizing the operating windings of the switches that have been. closed, provide means whereby when each. switch is closed its operating winding is rendered independent of said relay device.

In order to more particularly set forth the characteristic features of my invention as the same may be embodied in practice, I have diagrammatically illustrated in the accompanying drawing a system. in which my taincd by vari'us organizations of ele-' ments.

' 1 shall now proceed to ,describe 'the sysi illustrated in the accompanying draw- 7 -5, 5 and 5 The auxiliary contact 4 controls the circuit 0t winding 2, and the auxiliary contact 4 controls the circuit of wind-- ing 2 The circuits of the windings 2, 2 and 2 are also controlled by relay switches 6, 6" and 6 respectively, which relay switches are operated by electromagnetic winding 7, which is connected in circuit in series with the motor armature. I

The motor is provided with an armature va, and a field winding 7. The motor curcuit is controlled by means of the main switch 8, which is operated by electromagnetic winding 9. The main switch is provided with an auxiliary contact 10 and an interlocking contactlL. The braking circuit which extends across the motor armature is controlled by means of a braking switch 12, which is operated by an electromagnet 13. The braking switch 12 is provided with an auxiliary contact 14 and interlocking contact 15. The motor armature or the machinery driven by the motor is connected to a mechanical brake. The brake I have diagrammatically illustrated in the drawing, has a wheel 16 having thereon a brake band 17. The brake band is connected to a stationary support 18, and to a lever 19, which is pivoted upon said support. The .lever carries a weight 20. The weight normally depresses the lever and causes the brake band 17 to be tightened around the brake wheel 16, thereby holding the armature a, or the machinery connected to said armature. The brake is released by means of an electro-magnetic winding 21, which serves to raise the lever 19. The circuit of this winding is controlled by means of a brake relay switch 22, the operation of which is controlled by two electro-magnetic windings 23 and 24.

The operation of the controller is directed by means of a master switch 25, which may be of the drum type. On one side of the drum is mounted a, plurality of contact segments 26, 26, 26 and 26. On the other side a plurality of contact segments 27, 27 and 27 Between these segments is mounted a plurality of stationary contacts 2s, 28, 28', 2s. and 28 The line from which current is obtained is provided with a line switch 29. If the master controller 25 be turned to the right, segments26, 26?, 26 and 26 will engage contacts 23, 28 28 and '28 respectively. Circuit will thus be closed from the positive line through conductor 30, contact 28,

I from the -as the current remains abnormal.

through conductor 36, switch 8, conductor" 37, conductor 38, armature a, conductor 39, series relay winding 7, resistance sections 3*, 3 and 3, conductor 40 to the negative line 35. The motor will thus be started with all the starting resistance 3, 3" and 3 in circuitwith its armature. The motor field circuit extends from the positive line through conductor 30, conductor 41, shunt field winding f, conductor 42 to the negative line 35. The brake relay switch 22 will be closed by electro-magnetic winding 23, which winding is connected in circuit 30, contact 28, segment 26, segment-26, contact 28 ,'winding 23, thence through conductor 43, conductor 42, to the negative line. Accordingly switch 22' will be closed completing the circuit through solenoid 21 which will thus be energized and raise the lever 19, thereby releasing the mechanical brake. When switch 8 is closed the circuit for winding 9 is completed by auxiliaryswitch 10 and conductor 57 connected to the negative line, switch independent of said interlocking contacts 5, 5 and 5*. The motor having now been started with all the starting resistance in circuit, the switches 1, 1" and 1 will be closed. successively, thereby removing the resistance sections 3, 3 and 3 from circuit, one after the other. The operating magnets 2, 2 and 2 of the resistance switches are all connected to the positive line through the master switch which establishes a circuit leading from the positive line over conductor 30, through contact 28, segment 26, segment 26", contact 28, conductor 44, to one of the of the windings 2, 2 and 2 The winding 2 is connected to the negative line through conductor 45, relay switch 6, conductors 46 and 34, to the negative line. Accordingly resistance switch 1 will be closed first, thereby short-circuiting resistance section 3, the short-circuit around said resistance section extending through conductor 47 and resistance switch 1. If the motor current be abnormal before the resistance switch 1 is closed, the series relaw magnet 7 will respond and open the relay switches. Accordingly, the circuit of winding 2 will be opened by relay switch 6 until the surge of current subsides, whereby resistance switch 1 will 'beprevented from closing so long When resistance switch 1 is closed, the auxiliary switch 4 is closed, thereby connecting windpositive line through conductor thus rendering said main terminals of each resistance switch 1 will not close.

pendent of said relay switch.

ing 2 to the negative side of the line by a circuit leading through conductor 48, relay switch 6, conductor 49, auxiliary switch 1, resistance switch 1 to the negative side of 5 the line. If the current be abnormal after resistance section 3 is removed from circuit the series relay magnet 7 will again respond. The circuit of winding 2 will thus be opened by relay switch 6. Hence, As soon as the current becomes normal again relay switch 6 will he closed, and accordingly winding 2 will become energized and close resistance switch 1. .When resistance 5 switch 1 is closed it'causes auxiliary contact 4 to connect winding 2 to the negativeline through auxiliary resistance switch 1, and accordingly relay switch 6 is short-circuited, whereby winding 2 is rendered inde- In consequence the resistance switch 1 will remain closed, notwithstanding the opening 0t relay switch 6, when the current again becomes abnormal. W hen resistance switch "1 closes, its auxiliary contact connects winding 2 to the negative line through conductor 50, relay switch 6 conductor 51, auxiliary contact 4:, resistance switch 1, and conductor 34. The auxiliary contact 4 connects winding 2 directly to the nega- 5 sistance switch 1 is closed its winding 2 is connected directly to't-he negative line, through auxiliary switch 4! and resistance switch 1", and accordingly relay switch 6 is short-circuitedand said winding is rendered independent of said relay switch.

When the resistance switches 1, 1 and 1 are closed interlocking switches 5, 5 and 5 are opened. The purpose of the interlocking contacts-will he hereinafter set forth.

If it is desired to stop the motor the mas-- ter controller is turned to the left, so that contacts 28, 28 and 2 are engaged by contacts 27, 27 and "27 respectively. Inasmuch as the circuit of winding 9 will be opened at contact 28", the main switch 8 will he opened, and inasmuch as the circuit of winding '23 of the brake relay switch is opened at contact 28, the winding 23 will be filciinergizcd. The brake relay switch 22, however, will not open as it will he held in a closed position by winding 24, which is connected across the armature a and is energized by the current developed in said armature. When the armature comes to rest and ceases to develop sutlicient current to energize winding 24:, the brake relay switch will be opened, and the mechanical lira-kc will he applied thereby firmly holding tholariualure against rotation. i lhen contact 28 pass from segment 26" to, segment 27", the controlling circuit leading to the operating windings 2, 2 and 2 of the resistance switcheswill be opened. Accordingly these switches will be opened and the resistance 3, 3 and 3* will be placed in circuit.

The braking switch 12 will now be closed by interlocking switches 5, 5 and 5", conductors 34 and 35 to the negative line. When braking switch v12 is closed the circuit through the winding 13 thereof is completed by auxiliary switch ll, switch 12 and conductor 56 to the negative line thereby rendering said braking switch independent of interlocking switches 5, 5, and 5". A closed circuit or loop in which is arranged the resistance 3, 3 and 3 is thus connected across the terminals of the armature a, which circuit extends from one terminal of the armature through conductor 38, conductor 37, conductor ,55, switch 12, conductor 56, conductor 35, resistance 3,-3 and 3 winding 7, conductor 39 to the other terminal of the armature. The motor will now become a generator, owing to the fact that its armature a will continue-to rotate for a while owing to the impetus it acquired while the motor was in operation. Accordingly the armature will send current through the closed loop, including the resistance. Such action causes the motor to act as a dynamic brake, and accordingly the armature will be quickly and smoothly brought to rest. The braking force that is exerted by the armature is proportional to its electrical load, which load depends upon the current which may flow through the closed loop. As the speed of the armature decreases, the braking current in the closed loop naturally tends to' decrease, and in consequence the bralring force exerted by the armature tends to decrease. Inasmuch as the windings 2, 2 and 2 are connected to the positive line through a path leading to said line through conductor 30, contact 28, segment 27, segment 27",, contact 28 and conductor 44-, the switches 1, 1 and l will current is abnormal before resistance switch 1 closes, the series relay magnet responds and thus prevents said resistance switch from closing until the current falls below a predetermined point; If after the switch 1 closes, the current again becomes abnormal the series relay magnet 7 will respond and prevent the switch 1 from closing so long as the current remains abnormal, and so on, the resistance switches operating successively and having the progressive operations thereof arrested whenever the current becomes abnormal. Accordingly the braking current will be prevented from rising above a predetermined limit, and at the same time will be proportioned at a hi-gh value throughout the braking period, thereby reducing the time required to bring the armature to rest. When the motor nearly comes to rest and ceases to develop suflicient current to energize winding 24, the relay brake switch 22 will be opened, and ac cgrdingly the mechanical brake will be app, 1e

Inasmuch as the interlockin switches 5, 5 and 5 are arranged in thG'CII'CUitS of the operating windings 9' and 13, it will be impossible for the-braking switch 12 or the main switch 8 to close, unless the resistance switches 1, 1 and 1 are open. Accordingly the motor circuit or the braking circuit can not be closed unless the resistance 3, 3 and 3 is first included in the armature circuit. Fu thermore, inasmuch as the interlocking switch 15 is in the circuit of the operating winding 9 and interlocking switch 11 is in the circuit of the operating winding 13, it will be impossible for the main switch 8 to be closed unless the braking switch 12 is open, and also it will be impossible for the braking switch 12 to be closed unless the main switch 8 is open.

The use of the motor as a dynamic brake is advantageous because of the fact that it is not subjected to wear during the braking action and accordingly does not require adjustment in order to bring the load to rest in a given period. Inasmuch as the mechanical brake is not applied until the motor nearly comes to rest it is subjected to very little wear and accordingly very seldom requires adjustment.

I am, of course, aware that my invention is capable of application in various relations and that it may be used on various classes of machinery where it is necessary to use a brake in bringing the machine to rest, as is usually the case with machines that have to be started and stopped at frequent intervals.

Having thus described my invention what I claim as new anddesire to secure by Letters Patent, is: l

1. In a controller for electric motors, in

combination, means for closing the motor act as a dynamic brake and a single automatic device for energizing said electromagnetic winding upon closure of the motor circuit and maintaining the same energized until the speed of the motor decreases to a predetermined degree under dynamic braking action.

2. The combination with a controller for starting and stopping an electric motor, a mechanical brake, means for closing the motor circuit, electromagnetic means for maintaining said brake inoperative while the motor circuit is closed, means for disconnecting the motor from circuit, electromagnetic means for connecting a circuit across the terminals of the motor armature, means to energize said last mentioned electromagnetic means after the motor circuit is interrupted, and electromagnetic means connected in circuit for maintaining said brake inoperative until the armature approaches a condition of rest.

3. In a controller for stopping an electric motor, in combination, means for opening" the motor circuit, electromagnetic means for connecting a circuit across the terminals of the motor armature, means for energizing said electromagnetic means after the motor circuit is opened, a mechanical brake, an elcetro-responsive device adapted to maintain said brake inoperative, and an electro magnetically operated switch for controlling the circuit through the winding of said electro-responsive device, the winding of said electromagnetically operated switch being connected across the terminals of the armature. i

4. In a motor controller, in combination,

a variable resistance connected across theterminals of the motor armature, means for arresting the removal ot said resistance from circuit when the armature current rises above a predeterminedvalue, a mechanical brake operatively connected with said armature, and electroresponsive' means energized upon closure of the motor circuit for rendering said mechanical brake inoperative until the current through said armature falls to a predetermined point.

5. In a motor controller, in combination, a variable resistance connected across the terminals of the motor armature, means for removing said resistance from circuit gradually as the armature speed decreases, means forarresting the removal of said resistance from circuit as the armature circuit rises above a predetermined value, a mechanical brake operatively connected with said armature, electro-responsivc means responsive to the armature current for maintaining said brake inoperative until the armature current falls to a predetermined value, said electro ually as the armature speed decreases, means for arresting the removal of said resistance from circuit when the armature current rises above a predetermined value, a mechanical brake operatively connected with said armature, electro-responsive means responsive to the armature current for maintaining said brake inoperative until the armature current falls to a predetermined value, said electroresponsive means having a winding permanently connected across the terminals of the motor armature.

7. In a controller for stopping and starting an electric motor, a, variable resistance, means for removing said resistance from circuit gradually, means for .arresting the removal or said resistance from circuit when the armature current rises above a prede-- termined value, a brake operatively connected with said armature, an electro-responsive means for maintaining said brake inoperative while the motor circuit is closed,

- means for connecting said resistance in series with the motor, means for connecting said resistance across the terminals of the armature, and means, for rendering said electro-responsive means responsive to the armature current when said resistance is connected in shunt therewith.

8. In controller for starting and stopping a motor, in combination, a variable resistance, a plurality of electro-magnetically t ance switches for removing said resistance from. circuit gradually, a series relay switch for prevei'iting the too rapid removal of said resistance from circuit, a main switch for connecting said resistance in series with the motor armature, a braking switch for coi'inecting said resistance across the terminals of the armature, a mechanical bralre, an electroresponsive device for maintaining said brake inoperative, an electro-magnetically operated switch for controlling the circuit throu a said electroresponsive device. said electro-mechanically operated switch having two windings, one of said windings being energized when the motor circuit is closed, the other of said windings being energized. when said bral'- ing switch closed.

9. In a motor starting and stopping device, in combination, a variable resistance, a plurality o? electriwmagnetically operated resistance switches for removing said istance from circuit gradually, a series relay switch for preventing the too rapid removal of said resistance from circuit, a main switch for connecting said resistance in series with the motor armature, a braking switch for connecting said resistance across the terminals of the armature a mechanical brake, an electro-responsive' evice. for maintaining said brake inoperative, an electro-niagnetically operated switch for controlling the circuit through said electro-responsive device, said electro -magnetically operated switch having two windings one of said windings being energized when the motor circuit is closed, the other of said windings being on ergized when said braking switch is closed, and a master controller for controlling all of said switches.

10. In a motor starting and stopping device, in combination, a variable resistance, a plurality of electro-magnetically operated resistance switches for removing said resistance from circuit gradually, a series relay switch for preventing the too rapid removal of said resistance from circuit, a main switch for connecting said resistance in series with the motor armature, a braking switch for connecting said resistance across the terminals of the armature, interlocking means necessitating the insertion of all of said resistance in circuit before either said main switch or said braking switch can be operated and for preventing either of said switches being operated-unless the other is lllOpCl'fltlVt), a mechanical. brake, an electroresponsivc device for maintaining said brake inoperative, an electro-magnetically operated switch for controlling the circuit through said electro-responsive device, said electro-magnetic switch having two windings, one of said windings being adapted to cause said switch to close when the motor circuit is closed, the other of said windings being adapted to cause said switch to close the circuit through said device when the braking switch is closed, and a master controller for controlling all of said switches.

11. In a motor controller, in combination, means for closing the motor circuit, means for establishing a dynamic braking circuit for the motor to stop the same, a mechanical brake, electroresponsive means for render 'lng said brake inoperative, and a single automatic switch for causing said electroresponsive means to respond upon closure of the motor circuit andto be maintained onergized until the motor speed decreases to a predetermined degree under dynamic braking action.

12. In a controller for electric motors, in combination, means for closing the motor circuit, means for establishing a dynamic braking circuitfor the motor, a mechanical brake, an electroresponsive winding for rendering said brake inoperative, an elect rore sponsive switch controlling the circuit of said winding, and circuit connections tor causing said switch to respond upon closure, of the motor circuit and for maintaining said switch energized after the dynamic braking circuit has been established.

13. In a controllerfor stopping an electric motor, means for connecting a variable resistance across the motor armature, means for automaticall and gradually removing said resistance f i om circuit, a mechanical brake, electroresponsive means for main- 0 taining said brake inoperative, and a single switch having two coils for controlling said electroresponsive means.

14:. In a controller for stopping electric motors, the combination with means for con necting a variable resistance across the moping an electric motor, in combination,

tor armature, means for automatically and gradually removing said resistance from circuit, a mechanical brake, elect'roresponsive means for controlling said brake, and a sin- 0 gle switch having two windings, one being connected across the motor armature for maintaining said brake inoperative until the motor approaches a condition of'rest.

15.-In a controller for starting and stopmeans forconnecting the motor to a source of supply, means-for connecting a circuit across the motor armature, a variable re- 0 sistancein the armature circuit, means for resistance from circuit, a mechanical brake, electroresponsive means for maintaining said brake inoperative, and a switch controlr ling said electroresponsive means having two windings, one adapted to be connected to the source of supply, and the other being connected across the motor armature for maintaining said brake inoperative until the 0 motor approaches a condition of rest.

16. In a controller for stopping an electric motor, in combination, means for conautomatically and gradually removing said necting a variable resistance in circuit across the motor armature, a plurality of electro magnetic switches for gradually removing said resistance from circuit, means for pre venting the too rapid removal of said resistance, a mechanical brake, and means for maintaining said brake inoperative until the motor approaches a condition of rest.

17. In a controller for stppping an clectric motor, in combination, .563118 for connecting a variable resistance lli gllfilllt across the motor armature, a plurality ofelectromagnetic switches for gradually removing said resistance from circuit, means -for preventing the too rapid removal of said resistance, a mechanical brake, clectroresponsive means for maiL-l'ainihg said brake inoperative, and a single switch having two coils for controlling said elcctroresponsive means.

18. In a controller for stopping an elec tric motor, in combination, means for connecting a variable resistance in circuit across the motor armature, a plurality of electro- -Inagnetic switches for gradually removing said resistance from circuit, means for preventing the too rapid removal of said resistance, a mechanical brake, el'ectrorcsponsive means for-maintaining said brake in operative, and a single switch having two coils for controlling said electroresponsive means, one of said coils being connected in circuit to maintain said brake inoperative until the motor approaches a condition of rest.

In witness whereof, I have hereunto sub-. scribed my name in the presence of two 2.1%

nesses.

CLARK T. HENDERSON Witnesses: F RANK H. HUBBARD, ALEXANDER H. LIDDERS. 

